FACILE SYNTHESIS OF 4-PIPERIDONES BY CONDENSATION OF AN ALPHA,BETA-UNSATURATED KETONE, AN ALDEHYDE AND AMMONIA - SYNTHESIS OF THE DENDROBATID FROG ALKALOID 241D

A one-step reaction of an alpha,beta-unsaturated ketone (3-penten-2-on e, 1), an aldehyde (decanal, 2) and an amine (ammonia) afforded mainly the cis-isomer of(+/-)-2-methyl-6-nonyl-4-piperidone (3). Sodium boro hydride reduction afforded as the major product (+/-)-cis,cis-4-hydrox y-2-methyl-6-nonylpiperidine (4), identical in NMR and IR spectra to t he (+)-piperidine 241D isolated from skin extracts of a dendrobatid fr og. The reaction was shown to be generally applicable for the synthesi s of 2,6-disubstituted 4-piperidones.